Analysis of the possible cytogenetic mechanism for overcoming hybrid lethality in an interspecific cross between Nicotiana suaveolens and Nicotiana tabacum

Abstract

Hybrid lethality is a type of reproductive isolation in which hybrids die before maturation, due to the interaction between the two causative genes derived from each of the hybrid parents. The interspecific hybrid of Nicotiana suaveolens × Nicotiana tabacum is a model plant used in studies on hybrid lethality. While most of the progeny produced from such a cross die, some individuals grow normally and mature. Separately, a technique for producing mature hybrids by artificial culture has been developed. However, the mechanism by which hybrids overcome lethality, either spontaneously or by artificial culture, remains unclear. In the present study, we found that some hybrids that overcome lethality, either spontaneously or by artificial culture, lack the distal part of the Q chromosome, a region that includes the gene responsible for lethality. Quantitative polymerase chain reaction results suggested that the distal deletion of the Q chromosome, detected in some hybrid seedlings that overcome lethality, is caused by reciprocal translocations between homoeologous chromosomes. The results showed that chromosomal instability during meiosis in amphidiploid N. tabacum as well as during artificial culturing of hybrid seedlings is involved in overcoming hybrid lethality in interspecific crosses of the genus Nicotiana.

Understanding and overcoming hybrid lethality in seed and seedling stages as barriers to hybridization and gene flow

“…In some cases, this can be attributed to the deletion of the entire chromosome or certain regions of the chromosome where causal genes for hybrid lethality are located ( Tezuka et al., 2010 ; Tezuka et al., 2012 ; Hancock et al., 2015 ). In hybridization between N. suaveolens and N. tabacum , deletion of the chromosomal region containing a hybrid seedling lethality gene could be caused by reciprocal translocations between homoeologous chromosomes of N. tabacum in viable hybrid seedlings obtained spontaneously very rarely as well as those obtained by tissue-culture ( Nakata et al., 2021 ). Nevertheless, other mechanisms may also be involved in the spontaneous generation of very rare viable hybrid seedlings.…”

Overdominant expression of related genes of ion homeostasis improves K+ content advantage in hybrid tobacco leaves

“…Nicotiana tabacum L. is a typical allotetraploid crop, a natural cross of two ancestors, Nicotiana sylvestris and Nicotiana tomentosiformis [32]. Hybrid dominance in intra-and interspecific tobacco varieties is prominent [33][34][35]. Heterosis has been widely studied for excellent performance in growth capacity, leaf yield, quality, plant height, and disease resistance of tobacco verities [34,[36][37][38].…”